The present invention disclosed herein relates to a reflective colorless optical transmitter used for optical communication.
Recently as the ultra high speed internet and various multimedia services are emerged, a fiber to the home (FTTH) technology has been actively developed for connecting a telephone company to a home with an optical fiber to provide mass information transfer. In order to implement the FTTH, various types of optical subscriber networks are required. In implementing the FTTH, the most important conditions are lowering cost as well as mass transfer. The passive optical network (PON) is excellent in network management and maintenance due to characteristics of passive devices and is economy since several subscribers share to use optical fibers.
In particular, since different wavelengths are respectively allocated to different subscribers in a wavelength-division multiplexed (WDM)-PON scheme, security and extensibility are high. However, a light source, such as an expensive distributed feedback laser diode (DFB LD), is necessary which has a different wavelength for each subscriber, and, for wavelength management, a specific light source having a different wavelength for each subscriber is required to be in stock in preparation for failure. Accordingly, price competitiveness is lowered. Therefore, a colorless optical transmitter is necessary as a WDM-PON light source. Recently, as necessity for a colorless optical transmitter operable in an ultra high speed of 10 Gbps or higher is surfaced, a semiconductor optical amplifier (SOA) into which a reflective optical modulator is integrated has be massively researched.
Typically, in a PON, a reflective colorless optical transmitter is positioned in an optical network unit (ONU), and an input carrier light source for the reflective colorless optical transmitter is positioned in an optical line terminal (OLT). Accordingly, since optical power of the input carrier for the reflective colorless optical transmitter has different attenuations along various paths of an optical distribution network including an array waveguide grating, an optical splitter, and a feeding fiber, it is important that a reflective colorless optical transmitter generates a modulation signal without distortion even in a wide input optical power range.